Therapeutic catheters are frequently introduced into the body by means of guiding catheters. In the case of intravascular procedures, the system containing the guiding catheter must be closed and pressurized to prevent the development of blood loss and hemodynamic compromise during the performance of the therapeutic procedure. To permit the introduction and exchange of therapeutic catheters within this relatively closed system, several adapters have been created that: (1) provide a port of entry for the therapeutic catheter and (2) provide a seal between the therapeutic catheter and the aforementioned system. The seal functions to limit the amount of systemic pressure and/or blood loss that transpires during the course of introducing or exchanging a therapeutic catheter within the guiding catheter system. These adapters all contain a side port that can be used for various purposes, such as monitoring intravascular pressures, flushing the guiding catheter system, evacuating blood clots from the system, and the like. Because of their configuration, these adapters are called Y-adapters. Although similar in many respects, these devices differ with respect to the design of the sealing element or check valve.
One type of sealing element consists of a membrane, disposed perpendicular to the axis of the Y-adapter, containing a central perforation, that accommodates the therapeutic catheter. Initial insertion of the therapeutic catheter through the perforation stretches the membrane slightly to create an effective seal. An example of this type of Y-adapter is the model 006057 introduced by USCI Bard Catheter Systems of Billerica, MA.
There exist several functional limitations intrinsic to this type of sealing design among them the following: (1) the seal cannot be adjusted to accommodate to the various configurations and dimensions of current generation catheters, (2) the seal cannot function properly following removal of the therapeutic catheter contained therein (a circumstance that invariably transpires during the process of exchanging therapeutic catheters, a common occurrence during the course of an angioplasty) and (3) the seal tends to deteriorate following the repeated introduction of catheters through the membrane. In addition, the use of Y-adapters containing membrane sealing devices frequently exposes the therapeutic catheter to considerable trauma during the process of introducing and removing the catheter across the membrane.
Because of these limitations, among others the use of Y-adapters containing membrane sealing devices has been largely replaced by the use of adapters containing adjustable O-ring sealing devices. There currently exist two such devices, model 23242 manufactured by Advanced Cardiovascular Systems (ACS) of Mountain View. and the dual valve rotating Y-adapter, catalogue number Y-7200 manufactured by American Edwards of Irvine, Calif. California. In the case of these devices, the deformable O-ring is mounted coaxial with the main bore of the adapter, within a threaded element Rotation of the threaded element, relative to the adapter compresses the deformable O-ring resulting in a progressive reduction in the luminal dimensions of the O-ring. A seal is created when the luminal dimensions of the O-ring approximate the corresponding outer dimensions of the therapeutic catheter installed therein. This O-ring design offers several advantages relative to the aforementioned membrane design View, Calif. it can be adjusted to maintain an effective seal regardless of the presence, absence, or dimensions of the catheter installed therein.
Despite these advantages, the seal created by the O-ring does not function automatically. As a result the use of adapters containing this type of sealing device requires continuous attention during the process of therapeutic catheter introduction, manipulation and withdrawal, a circumstance that is both distracting to the operator and counterproductive to the performance of an angioplasty, a complex and mentally demanding procedure. In addition, the O-ring design does not permit the maintenance of a satisfactory seal throughout the process of introducing or removing the therapeutic catheter, regardless of the attentiveness of the operator. For example, the insertion of a therapeutic catheter within a Y-adapter containing an O-ring sealing device requires the operator to adjust the luminal dimensions of the O-ring to accommodate the therapeutic catheter dimensions before introducing the catheter a circumstance that invariably compromises the sealing capacity of the device and permits considerable fluid loss (e.g.. blood loss) from the pressurized system. A similar circumstance transpires during the course of removing a therapeutic catheter from the Y-adapter. Thus, blood loss inevitably occurs during the process of both introducing and removing therapeutic catheters from pressurized guiding catheter systems containing O-ring sealing devices. Although it is tempting to speculate that the dimensions of the O-ring could be adjusted to permit the gradual introduction of the therapeutic catheter with minimal interruption of the seal, it must be recognized that this circumstance exposes the relatively delicate and expensive therapeutic catheter to considerable potential trauma -- an unacceptable circumstance.
In short, the use of all currently available Y-adapters, during the performance of an angioplasty, or similar therapeutic procedure, wherein a therapeutic catheter must be installed within a relatively closed and pressurized guiding catheter system, invariably results in blood loss from the system, during the process of catheter introduction, manipulation, exchange and withdrawal. Although blood loss per se constitutes an adverse potential of these devices for the patient, it must be recognized that this circumstances also directly exposes the operator to potential contaminants within the patient's blood stream. The accumulation of blood within the guiding catheter system, an inevitable consequence of backbleeding through the Y-adapter check valve, also permits the formation of blood clots within the guiding catheter system, that could precipitate a stroke or heart attack, if inadvertently dislodged and introduced into the patient's circulation (which is in direct communication with the guiding catheter system). The presence of blood within the translucent Y-adapter also obscures the lumen within the adapter, further complicating the process of introducing the often small and delicate therapeutic catheters within the confines of the device.
To limit the extent of back-bleeding sustained during the process of introducing and removing the therapeutic catheter through the O-ring sealing device, a relatively stiff conical valve has been installed within the main bore of the American Edwards device, coaxial with, and proximal to, the O-ring check valve. Although this arrangement is partially effective this combination of valves: (1) does not function automatically, (2) does not provide an adequate seal throughout the process of introducing and removing a therapeutic catheter and (3) it exposes the therapeutic catheter to an increased risk for potential trauma during the process of manipulating the catheter across both valves in either direction. This latter circumstance derives from the fact that the presence of the in-line conical valve substantially contributes to the intrinsic resistance of the device to the passage of a therapeutic catheter. As a result substantially increased force must be applied to manipulate therapeutic catheter through this device relative to the ACS adapter.
Because the Y-adapter is interposed between the patient and the transducers used to monitor the patient's hemodynamic status, within the guiding catheter system, disruption of the Y-adapter seal profoundly compromises the operators ability to monitor the hemodynamic status of the patient. Because the seal must be compromised during virtually every aspect of the angioplasty procedure (e.g., therapeutic catheter introduction, withdrawal and exchange) to permit manipulation of the therapeutic catheter relative to the Y-adapter, and because this circumstance substantially impairs the operator s ability to assess the status of the patient during the procedure, most operators have become accustomed to intermittently interrupting the angioplasty procedure in order to close the seal temporarily and thus reassess the patient's hemodynamic status, an approach that contributes to the duration, complexity and potential risk of the angioplasty procedure.
In addition to the aforementioned functional limitations of conventional Y-adapters, it must be recognized that these devices frequently bind onto the therapeutic catheters installed therein (thus compromising the operator s ability to determine the amount of resistance incurred by the distal aspect of the catheter during introduction of the catheter across a stenotic lesion). Furthermore, all currently available Y-adapters: (1) contain considerable dead space that permits the accumulation of blood clots. (2) provide inadequate seals when used in conjunction with asymmetric systems (e.g., monorail systems) and (3) frequently permit the inspissation of air bubbles within the guiding catheter system.
In summary, there currently exists no Y-adapter that contains a sealing element that: (1) functions automatically, (2) functions satisfactorily throughout all phases of catheter introduction and withdrawal and that (3) generates minimal resistance to catheter introduction.
Although the primary application of the device described herein is directed to a Y-adapter that meets these criteria, it must be recognized that this invention can be modified into the configuration of an intravascular sheath (such as one made by Cordis Corporation of Miami, Florida as Catheter Sheath Introducer System) that can be used to expedite the percutaneous introduction of a variety of both therapeutic and diagnostic catheters within the vascular system with minimal resistance, blood and/or pressure loss. Although considerably different in appearance the components of a sheath and a Y-adapter are substantially similar. In the case of sheaths, the sealing element consists of an elastomeric gasket that circumferentially contains the catheter installed therein. Although the seal created by the gasket is generally effective, the resistance generated by this sealing element to the passage of a catheter is generally considerable. In fact, this type of sealing element occasionally binds to the catheter contained therein, thus substantially compromising the operator's ability to complete the intended procedure. In addition the gasket check valve tends to leak when crossed with simply a guide wire or small caliber catheter. This latter circumstance derives from the fact that the leaflets of the gasket check valve are designed to conform to the outer surface of a catheter of conventional dimensions. The insertion of a guide wire or small catheter across the check valve of a conventional sheath results in incomplete coaptation of the leaflets and hence incompetence of the valve.